After sequential lysis of the crosslinked cells in Lysis Buffer 1 and Lysis Buffer 2, the nuclear pellet was sonicated in Lysis Buffer 3 with a probe sonicator (Fisher Scientific Model 705 Sonic Dismembrator) at output level 55 (27–33 W) for 16 cycles with each cycle constituting of a 30 sec sonication on followed by a 60 sec off. For each ChIP, 100 μL Protein G Dynabeads (Invitrogen, 10003D) slurry and 10 µg of antibody was used. Chromatin incubation with antibody was carried out at 4°C with end-to-end rotation for 4-6 hours. DNA was quantified using the Quant-iT PicoGreen dsDNA Assay (Thermo Fisher Scientific, P11496). Libraries were prepared with the KAPA HyperPrep Library Kit (Roche, 07962363001) and analyzed for insert size distribution with the High Sensitivity DNA Kit (Agilent, 5067–4626) on a 2100 Bioanalyzer or the High Sensitivity D1000 ScreenTape Assay (Agilent, 5067–5584, 5067–5585, 5067–5587, 5067–5603) on a 4200 TapeStation. Libraries were quantified using the Quant-iT PicoGreen dsDNA Assay. HiSeq 2500, HiSeq 4000, or NovaSeq 6000 System (all from Illumina) was used.